Centrifugal classifier

ABSTRACT

A centrifugal classifier for sorting suspensions of fibrous materials has a housing with an intake defined in the upper region thereof. A stationary sieve basket is arranged with its axis vertically oriented in the housing and defines a plurality of perforations of a predetermined size. A rotatable sieve basket is mounted adjacent and coaxial with respect to the stationary basket and extends beyond the upper edge of the stationary basket to the vicinity of the intake. A plurality of perforations are also defined in the rotatable basket, the perforations in the lower region being of a predetermined size larger than the perforations in the stationary basket and the perforations in the upper end being of a predetermined size larger than the perforations in the lower region of the rotatable basket. The suspension flows from the largest to the smallest perforations.

United States Patent [151 3,677,402 Holz 1 July 18, 1972 [54] CENTRIFUGAL CLASSIFIER 945,317 6/1956 Germany ..209/270 [72] Inventor: Holz, Reutlingen-Betzingen, Ger- Primary Examiner .rim R Miles 7 y Assistant Examiner-William Cuchlinski, Jr. [73] Assignee: Hermann Finckh Metalltuch-und Maschin- Attorney-Spencer & Kaye enfabrik, Reutlingen, Germany 22 Filed: Sept. 17,1970 [57] ABSTRACT Appl. No.: 73,021

Foreign Application Priority Data References Cited FOREIGN PATENTS OR APPLICATIONS Germany ..209/306 A centrifugal classifier for sorting suspensions of fibrous materials has a housing with an intake defined in the upper region thereof. A stationary sieve basket is arranged with its axis vertically oriented in the housing and defines a plurality of perforations of a predetermined size. A rotatable sieve basket is mounted adjacent and coaxial with respect to the stationary basket and extends beyond the upper edge of the stationary basket to the vicinity of the intake. A plurality of perforations are also defined in the rotatable basket, the perforations in the lower region being of a predetermined size larger than the perforations in the stationary basket and the perforations in the upper end being of a predetermined size larger than the perforations in the lower region of the rotatable basket. The suspension flows from the largest to the smallest perforations.

5 Clains, 2 Drawing Figures Patented July 18, 1972 INVENTOR. Holz Emil ATTORNEYS CENTRIFUGAL CLASSIFIER BACKGROUND OF THE INVENTION The present invention relates to a centrifugal device for suspensions of fibrous materials having a perpendicularly disposed sieve basket and a concentric drum which rotates closely therearound and which is provided with perforations,

an intake being provided in the upper region of the centrifugal- SUMMARY OF THE INVENTION Within the scope of this recognition, it is among the objects of the present invention to maintain the number of sieve baskets while providing more sorting stages.

To achieve this and other objects, the present invention provides a drum designed as a sieve basket revolving with respect to a pedestal and extending over a stationary sieve basket by an amount which permits it to extend into the area of an intake. The perforations in this upper portion of the drum are larger than those in the lower portion through which the material subsequently flows out of the drum, and the perforations in the sieve baskets through which the material flows thereafter are again smaller than the last mentioned perforations. The housing of the device below the upper portion of the rotating sieve basket and outside of the range of the sieve baskets is provided with a coarse material trough and an associated discharge pipe.

In this type of construction, two sieve baskets achieve the effect of a classification through three sieve baskets. Furthermore, the rotating sieve basket takes over the task of the cleaning vanes otherwise required at the stationary sieve baskets.

Two further classification stages which can be realized with little effort result when, according to a further advantageous feature of the present invention, an annular baffle member is inserted into the intake stream between the upper portion of the rotating sieve basket and the intake. This baffle leaves free at its upper end a passage to the upper portion of the rotating sieve basket, and its lower portion extends into a course material trough.

With the use of such an annular baffle, the effect on the heavy components of the incoming material is the same as an impermeable partition from which they are directed directly downwardly into the coarse material trough. In the suspension which flows over the upper edge of the annular bafile, the larger components then come under the centrifugal influence of the protruding upper portion of the rotating sieve basket or the suspension stream which encloses this portion and rotates therewith. The coarse components are here forced away toward the inner surface of the annular baffle and also reach the coarse material trough along this wall as they move downward.

The thus twice preclassified suspension is then sorted a third time in the coarse perforations of the upper portion of the rotating sieve basket through which it flows. Then the suspension reaches the lower region of the rotating sieve basket and is sorted a fourth time when it flows in the opposite direction through the finer perforations in this lower portion and finally, when it flows through the finest perforations in the stationary sieve basket directly enclosing the rotating sieve basket, it is sorted a fifth time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation, cross-sectional view of a centrifugal classifier according to the present invention.

FIG. 2 is a cross-sectional view taken generally along the line 2- 2 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT An annular chamber 14 is defined by a wall 42 in a housing 13 which stands on a base 11 and is closed off by an upper cover 12. A tangentially directed intake pipe 15 is also provided, as well as a conical chamber 16 which is defined by a wall 43, and joins with a radially disposed outlet pipe 17. This conical chamber 16 is covered toward its center axis by a stationary sieve basket 18. Within the stationary sieve basket 18, a second sieve basket 19 with an upper region 19' and a lower region 19" is arranged to rotate in a close relationship with respect to the stationary sieve basket. A support plate 21 is provided for basket 19, which plate 21 is fastened to a driven shaft 20 and covers the basket 19 at the top of its upper region 19'. The shaft 20 is mounted on an inner base, or pedestal, 22 of housing 13 and can be driven by a suitable drive disc, e. g. a pulley 42, rotatably mounted in the lower base 11. Any suitable, known means, such as a motor driven belt (not shown), may be used to rotate pulley 42.

The rotating sieve basket 19 preferably rotates with very little clearance between it and the stationary sieve basket 18. A plurality of clearing vanes 23 are firmly connected in a know manner to the base 22 and extend to the vicinity of the inside of the rotating sieve basket. For simplicity, only one of these clearing vanes 23 is shown in the drawings, but it is to be understood that others are arranged about base 22 in a similar manner. At the bottom of the annular chamber 14 is a coarse material trough 24 is provided, and at the foot of the base 22 that is, below basket 19 a slop material trough 25 is arranged. Each trough 24, 25 has an associated outlet pipe 26 (FIG. 2) or 27, respectively, for periodically discharging the collected materials. conical portion of the annular bafile 28 extends to the vicinity of cover 12 of housing 13, where it also leaves a passage through which the incoming suspension reaches the upper portion of the rotating sieve basket 19 after it has been downwardly deflected. This upper portion of the rotating sieve basket 19 is an extended portion which extends beyond the upper edge of the stationary sieve basket 18, and its supporting plate 21 is arranged adjacent to cover 12 of housing 13. The direction of rotation of sieve basket 19 is indicated by arrow A (FIG. 2). The direction of flow of the suspension and its components within the classifier is indicated by smaller arrows which will be explained later, while the locations of the different sorting, or classification, stages are marked 1 through V.

OPERATION Arrows 30 (FIGS. 1 and 2) indicate the tangential influx direction of a suitable, known suspension which is passed under pressure through intake 15. The suspension is supplied to intake 15 from any suitable, known source (not shown).

The heavy components of the suspension are disposed in the lower region of the flowthrough cross section of intake 15 and, therefore, brush along the cylindrical lower portion of baffle 28. Due to their weight, they sink lower and lower and finally reach trough 24. This is shown in FIG. 1 by arrow 31 in sorting stage I. At the conical upper portion of the baffle 28, the tangentially inflowing suspension is forced away in an upward direction, as indicated in FIG. 1 by arrows 32. It finally passes over the upper edge of the baffle 28 and through the gap remaining between baffle 28 and cover 12 and reaches the inner region of the bafile 28, because it is deflected in a through pipe 26 (arrow 39 in FIG. 2). The particles held back from the sieve perforations of basket 19 also reach trough 24. This is shown in FIG. 1 by arrows 40 in stage III. The perforations in the upper portion of the rotating sieve basket 19, however, are selected to be of such a size that they can not be plugged up by the suspension, but that flowthrough is always assured (arrows 41).

The suspension reaching the interior of the rotating sieve basket 19 as shown by arrows 41 in FIG. 1 is held in circulation by the basket 19 and then tangentially flows out when it flows out of basket 19 through the finer perforations in the lower portion of the sieve basket 19. This is shown in FIG. 1 by arrows 35. It then comes with its components to the edges of the even finer perforations of the stationary sieve basket 18, where further finer impurities are deposited, and flows therethrough (arrows 35). The particles held back by the lower portion of rotating sieve basket 19 and sieve basket 18 flow in the direction of arrows 36 (sorting stage IV) and 36a (sorting stage V) respectively into the trough 25 and are extracted from there through discharge pipe 27 (arrow 37 in FIGS. 1 and 2).

The completely classified suspension leaves the housing 13 through outlet pipe 17 (arrow 38).

in the drawing, the respective sieve perforations are shown only schematically by white spaces of varying sizes, which should not be considered as being to scale, particularly since the perforations may be, for example, either round or slitted and could possibly also have a cross section which varies over their fiowthrough length.

it will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

I claim:

1. Centrifugal classifier for sorting suspensions of fibrous materials, comprising, in combination:

a. a housing having an upper region with a periphery;

b. an intake in the periphery of the upper region of said housing;

c. a stationary sieve basket arranged in said housing to have a vertically oriented axis and defining an upper edge and a plurality of perforations of a predetermined size;

d. a rotatable sieve basket mounted adjacent, inside and coaxially with respect to said stationary basket and having an upper region with an extended portion extending beyond the upper edge of said stationary basket to the vicinity of said intake and a lower region, said rotatable sieve basket defining a plurality of perforations, the perforations in the lower region of said rotatable basket being of a predetermined size and larger than the perforations in said stationary basket and the perforations in the upper region of said rotatable basket being of a predetermined size and larger than the perforations in the lower region of said rotatable basket so that a suspension may flow from the largest perforations to the smallest perforations, and material outlet means in said housing.

2. The centrifugal classifier defined in claim 1, further including a coarse material trough and an associated discharge pipe arranged outside of said sieve basket and below the extended portion of said rotating sieve basket to receive coarse material to large to pass through the perforations in said extended portion.

3. The centrifugal classifier defined in claim 2, further including an annular bafile member arranged in said housing between said intake and said extended portion, said baffle member having an upper portion defining an upper edge which cooperates with a portion of said housing to define a passage between said intake and said extended portion, and further having a lower portion defining a lower edge and arranged to extend into said coarse material trough.

4. The centrifugal classifier defined in claim 3, wherein said annular bafile member has a cylindrical lower portion and a conical upper portion.

5. The centrifugal classifier defined in claim 4, further including a slop material trough and an associated discharge pipe arranged below said rotatable sieve basket for receiving material too large to pass through the perforations in the lower region of said rotatable sieve basket and the perforations in said stationary sieve basket. 

1. Centrifugal classifier for sorting suspensions of fibrous materials, comprising, in combination: a. a housing having an upper region with a periphery; b. an intake in the periphery of the upper region of said housing; c. a stationary sieve basket arranged in said housing to have a vertically oriented axis and defining an upper edge and a plurality of perforations of a predetermined size; d. a rotatable sieve basket mounted adjacent, inside and coaxially with respect to said stationary basket and having an upper region with an extended portion extending beyond the upper edge of said stationary basket to the vicinity of said intake and a lower region, said rotatable sieve basket defining a plurality of perforations, the perforatIons in the lower region of said rotatable basket being of a predetermined size and larger than the perforations in said stationary basket and the perforations in the upper region of said rotatable basket being of a predetermined size and larger than the perforations in the lower region of said rotatable basket so that a suspension may flow from the largest perforations to the smallest perforations, and material outlet means in said housing.
 2. The centrifugal classifier defined in claim 1, further including a coarse material trough and an associated discharge pipe arranged outside of said sieve basket and below the extended portion of said rotating sieve basket to receive coarse material to large to pass through the perforations in said extended portion.
 3. The centrifugal classifier defined in claim 2, further including an annular baffle member arranged in said housing between said intake and said extended portion, said baffle member having an upper portion defining an upper edge which cooperates with a portion of said housing to define a passage between said intake and said extended portion, and further having a lower portion defining a lower edge and arranged to extend into said coarse material trough.
 4. The centrifugal classifier defined in claim 3, wherein said annular baffle member has a cylindrical lower portion and a conical upper portion.
 5. The centrifugal classifier defined in claim 4, further including a slop material trough and an associated discharge pipe arranged below said rotatable sieve basket for receiving material too large to pass through the perforations in the lower region of said rotatable sieve basket and the perforations in said stationary sieve basket. 